In the first scene of Amour, firemen break down the front door of a Paris apartment and find a bedroom door sealed to discourage entry. Inside is the corpse of an elderly woman, her hands folded, flower petals wreathing her head.

The Austrian filmmaker Michael Haneke might have been chosen to be the chief prosecutor of modern man’s sins. His relentless depiction of the inhumanity to which civilized people can descend has raised cries of cinematic sadism. No one, however, disputes his mastery of camera mood in the modern psychodramas The Piano Teacher (2001) and Caché (2005) and the period epic The White Ribbon (2009), which portrays collective guilt in a German town 20 years before the rise of Hitler.

Because all three films premiered and won prizes at Cannes, the debut of Haneke’s latest work was welcome news to festivalgoers. The director did not disappoint. Amour (the French title will be retained when the film is released in the U.S. later this year by Sony Pictures Classics) is Haneke of the highest order. Amour possesses many of the filmmaker’s touchstones: an austere, majestic visual style, a central couple whose names are some variation of George and Anne, an enclosed setting that allows no exit for either the characters or their demons, and an abrupt act of violence. The difference here is the compassion that Haneke affords the two people in this story, and the love, not twisted or ironic, they show each other.

Georges (Jean-Louis Trintignant) and Anne (Emmanuelle Riva), both in their eighties, are retired music teachers. They are first seen together in the audience of a concert given by one of Anne’s former pupils. Typically, Haneke insists that the viewer search for his main couple; as in the climactic scene in Caché, which requires some detective work to locate the clue to the film’s mystery, this shot does not direct the viewer’s eye to Georges and Anne. But once they are located, they dominate the film. Although Isabelle Huppert has a few scenes as their concert-performer daughter Eva, and a half-dozen others appear briefly, Amour is basically a two-character drama — and, above all, a love story, Haneke-style.

They return from the concert, to their home (the apartment shown in the first scene) and find that the front lock has been damaged, perhaps by a burglar. Anne is troubled, Georges placid. “Imagine we’re in bed and someone breaks in,” she says, and he shrugs, “Why should I imagine that?” Over the next two hours Georges will prove that no outsider can break the cocoon he must create for his beloved.

At breakfast, when he expects Anne to fill an empty saltshaker, she doesn’t respond, and for several minutes her mind is a blank slate. Haneke builds the suspense with Hitchcockian precision: Georges’ concern as he wets a dish towel and applies it to her neck, and then, as in a panic he dresses in another room to go for help, his stricken surprise when he realizes that the kitchen faucet he left running suddenly stops. Georges returns to find that Anne is her vital self again, but, in another subtle shock, when she pours the tea she misses the cup.

Doctors say she suffered an obstruction of the carotid; but the surgery goes wrong, leaving the right side of her body paralyzed, with the imminent threat of another, more severe stroke that could rob her of all physical agility. As if rushing to review her life before the curtain falls, she reminds her husband that he was “a monster sometimes, but very kind” and asks him to retrieve a family album containing decades-old photographs of them and Eva. “C’est belle, la vie,” Anne says.

Having promised Anne that he will not take her back to the hospital, Georges becomes his wife’s hospice caregiver, with the help of nurses who tend to her three times a week. As an exercise for her impaired speech, Georges sings to her the traditional ballad “Sur le pont d’Avignon”; that stirs some participation. But often Anne’s mood is one of feral defiance. When Georges feeds his wife a few spoons of soft food or a sip of liquid, her eyes telegraph dark secrets. Is she horrified? Pleading? Empty? At a later feeding, he must pry open her mouth to force in the liquid. After she spits it out for the third time, he slaps her. Their roles now are willful child and exasperated father.

But they have been married for at least a half century — and in love, or loving each other, for at least that long. So, to a tough audience of one, Georges recapitulates aspects of their courtship, telling her stories of his youth, writing letters she will never be able to read. His devotion is as intense as any young man’s passion, and more enclosing because no one can interrupt it. Teen lovers may believe they are the only two people in the world, but this is the literal truth for Georges and Anne in their last days. The couple’s early love may have been a world blooming with possibility; in their last days together, love means shouldering the responsibilities of nurse, parent and bedside companion. Georges never complains of these duties, and would never default on his promissory note to Anne.

In a last anecdote, he recalls when as a child he was sent to summer camp. His mother had told him to send her a daily postcard, drawing flowers on it if he was happy, stars if unhappy. The camp did not suit him, and one day he sent a postcard covered with stars. Sometimes, Haneke suggests, life is flowers, and sometimes all stars. Georges’ life has become blanketed with stars — black holes of misery — even as Anne’s has gone blank. It is time for his final act of love, their last consummation.

This being a Haneke film, Georges and Anne do not appeal to religion for post-mortem deliverance; they act according to ethics mutually established in a lifetime together. Nor does Georges embrace his daughter’s expression of dismay, telling Eva, “Your concern is of no use to me.” He may accept practical help, which she does not offer, but not rote words of vexation. Haneke also strips Anne’s degeneration to its essence: the slackening of her features, the receding of understanding in her eyes, the withdrawal of any sign of life inside her.

Trintignant, 81, first attracted attention 56 years ago as the callow fellow seduced by Brigitte Bardot in …And God Created Woman before starring in the seminal ’60s films A Man and a Woman, The Easy Life, Z and The Conformist. Riva, 85, came to Cannes in 1959 as the nameless European in postwar Japan in Alain Resnais’ landmark Hiroshima mon amour. She and Trintignant never before appeared together in a feature film, but in the early scenes they are fully convincing as a lifelong couple: anticipating each other’s wants, engaging in playfully familiar badinage, sometimes nodding in silence at a shared memory.

Often playing passive roles, Trintignant here is a man who quietly takes charge of his wife’s siege; he whispers no love sonnets but is a man heroically devoted, determined to do justice to the final act of a long affair. Riva, in the 53-year journey from Hiroshima mon amour to Amour, has lost none of her startling commitment to the craft. Like actresses who play the flinty heroines of Samuel Beckett’s late plays, Riva must convey Anne’s personality through severely limited means: the slouch or starch in her body, the clarity or opacity in her eyes. Riva’s channeling of a woman who has lost memory and emotion — lost what some would call her soul — is a thrilling, draining emotional insight.

Haneke has often meted out punishment to his characters; in Amour he provides a reviving coda. The stern European master may be saying that true love can outlast the lives of the lovers. Whatever his message, the spell of this incandescent film will be an elevating memory. In the history of movies about love, Amour lasts forever.